Die Beeinflussung der elektrischen und mechanischen Eigenschaften von Wismut durch geringe Nickel-Zusätze

On the development of the galvanomagnetic amplifier with Bi Justi and Thuy had to overcome some technological difficulties. The greatest one was the large brittleness of the Bi-foils or -wires. However, in the last years Aske and Fitzpatrick have shown that the ductility of Bi can be enlarged by small amounts of some other metals like Ni. In this paper the authors give a thorough and systematic analysis of the electrical and mechanical properties of Bi-Ni-alloys. After a detailed discussion of the preparation methods metallurgical and X-ray investigations give a first glance into the structure of the alloys with Ni-contents final to 3,5 atomic per cent. Measurements of the magnetoresistance [Delta] [rho]/[rho]0 at room temperature and at the temperatures of liquid nitrogen and liquid hydrogen confirm generally the expectation of a large decrease with increasing Ni-concentration. Nevertheless at 77°K there is in increase in the [Delta] [rho]/[rho]0-values, possibly connected with a substitution mixed crystal of the otherwise unsoluble Ni in the Bi-lattice. The ductility of the Bi-Ni-alloys is tested with some kind of bend experiment on wires, produced by pressing the material under 120 kp/mm^2 through a nozzle of 1mm diameter. In contradiction to the statements of Aske and Fitzpatrick the ductility is a monotonic decreasing function with increasing Ni-content up to 0,7 weight% Ni, if the pressure form is not warmed up. However, if the production of the wires is realised at 90°C an alloy with 0,15 weight% Ni is more ductile than a specpure Bi-specimen in agreement with Aske and Fitzpatrick. Yet the absolute value of the ductility is lower than that of a pure Bi-wire, manufactured at room temperature. These experiments are further discussed in connection with some preliminary results on wires produced by cooling the nozzle to liquid air temperature. Summing up from a practical point of view these investigations show that the Bi is more convenient for a galvanomagnetic amplifier when it contains a small amount of Ni and the wire itself is manufactured by cold working below room temperature.